1. Field of the Disclosure
The present disclosure relates to a method and apparatus for measuring the thickness of any ice formed on a surface. Examples of the disclosure relate to capacitive sensors and/or the use of capacitive sensors to determine the thickness of any ice formed on a surface.
2. Description of the Related Art
Pipes and/or containers often contain fluids that include a small percentage of water, even if the fluid itself is not water. For example, aircraft fuels naturally include a small percentage of water. Under suitable, usually extreme, conditions, this water can freeze onto the walls of the vessels containing it, for example onto the insides of pipes. Aircraft are filled with fuel at ground level where the temperatures are relatively high but as the aircraft climbs to altitude the air temperatures surrounding the fuel tanks and pipes become colder. This leads to the possibility of ice forming on the walls of pipes and/or tanks containing the fuel.
This can have undesirable effects, such as reduced efficiency and/or reliability. Ice formation may be particularly problematic where thick layers of ice build up on surfaces. For example, where thick layers of ice build-up in pipes, the flow through the pipes may be restricted or, in extreme cases, even stopped. Furthermore, if a large build-up of ice is suddenly released, the released ice may block the fluid system at a downstream location. In extreme cases, where the fluid pipe is a fuel supply pipe, such a blockage may lead to temporary fuel starvation.
As such, it would be beneficial to be able to detect the thickness of the ice formed on a surface, for example within a fuel pipe, rather than just the presence of ice. For example, in a gas turbine engine application used as an aircraft engine, detection of ice build-up of a given thickness may allow appropriate action to be taken, for example by the pilot of the aircraft and/or by the aircraft systems. This may include, for example, increasing power to the engines while at high altitude to increase the fuel flow and vibration levels to release any ice that may have built-up and/or prevent further ice formation. If the ice is to be released by appropriate action, a decision (manual or automatic) could be taken as to when the ice should be released in order to have minimum impact, for example in the event of temporary fuel starvation. Purely by way of example, other possible action may include operating heaters to heat the fluid and/or the walls of the pipes to release the ice and/or melt it.